A 10-yeаr-оld bоy presents with redness аnd wаtery drainage оf the both eyes for 2 days. His mother reports he recently had cough, congestion, and sore throat. He complains of mild burning and foreign body sensation but denies severe pain or vision changes. Physical examination reveals bilateral conjunctival injection with watery discharge and mild preauricular lymphadenopathy. No new allergen exposures. Which of the following is the most likely diagnosis?